Question

The formula unit mass of $N{a}_{2}O$ is ____.

• A. 52
• B. 62
• C. 50
• D. 48

Answer 1

The correct option is B 62

Formula unit mass is the sum of the atomic masses of all the ions that form an ionic compound.

${\text{Na}}_2\text{O}$ is constituted by two ${\text{Na}}^{+}$ and one ${\text{O}}^{2-}$ ions.

Hence, the formula unit mass of ${\text{Na}}_2\text{O}$ = (2 $\times$ atomic mass of Na) + atomic mass of O = (2 x 23) + 16 = 62 u.